The first thing pilfered to fund Firebird production? (9,5)
I believe the answer is:
forbidden fruit
'the first thing pilfered' is the definition.
'to fund firebird production?' is the wordplay.
'production?' indicates an anagram (I've seen 'production' mean this).
'to'+'fund'+'firebird'='tofundfirebird'
'tofundfirebird' is an anagram of 'FORBIDDEN FRUIT'.
(Other definitions for forbidden fruit that I've seen before include "Apple" , "Something naughty not allowed" , "Illicit pleasure" , "Restricted as to diet?" .)